1. Field of the Invention
The present invention relates to a method of creating a substrate image being a reference in defect inspection on the basis of a plurality of picked-up substrate images, a method of performing defect inspection of a substrate on the basis of the created substrate reference image, an apparatus for creating a substrate reference image, a substrate defect inspection unit, and a non-transitory computer storage medium.
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-268203, filed in Japan on Dec. 7, 2012, the entire contents of which are incorporated herein by reference.
2. Description of the Related Art
In a photolithography process in a manufacturing process of a semiconductor device, for example, a series of treatments such as a resist coating treatment of applying a resist solution onto a wafer to form a resist film, exposure processing of exposing the resist film to a predetermined pattern, a developing treatment of developing the exposed resist film and so on are performed in sequence to form a predetermined resist pattern on the wafer. The series of treatments are performed in a coating and developing treatment system being a substrate treatment system including various treatment units that treat the wafer, transfer mechanisms that transfer the wafer and so on.
The wafer for which a series of photolithography processing has been performed in the coating and developing treatment system is subjected to a so-called macro defect inspection of performing inspection whether or not a predetermined resist film has been formed on the front surface of the wafer, or whether or not there is a scratch or adherence of foreign substance.
In such a macro defect inspection, while a mounting table on which the wafer is mounted is being moved illumination is applied to the wafer on the mounting table and, for example, an image pickup apparatus of a CCD line sensor picks up an image of the front surface of the wafer. Then, the picked-up image is subjected to image processing and the presence or absence of defects on the front surface of the wafer is determined (Japanese Laid-open Patent Publication No. 2009-216515). In the conventional defect inspection, the presence or absence of defects is determined by comparing the image of a wafer being a reference (reference wafer) and the image of a wafer to be inspected.
Incidentally, a so-called false defect that is not an actual defect but is determined as a defect because color unevenness occurs on the picked-up image of a substrate (substrate image) may occur in the defect inspection of the wafer. Therefore, the image of the wafer being the reference (reference image) is created by combining a substrate mage having color unevenness that may be determined as a false defect with the standard substrate image of a wafer having no defect. This makes it possible to take an element of the substrate image having the color unevenness into the reference image so as to prevent the color unevenness from being determined as a defect in defect inspection. In other words, the color unevenness is subjected to filtering to avoid the false defect.
A plurality of substrate images used for synthesis of the reference image are selected by an operator on the basis of the empirical rule from among images of a plurality of wafers which have been processed beforehand. In this case, the reference image to be created may differ depending on the level of skill of the operator. Therefore, a difference may occur in the result of defect inspection depending on the level of skill of the operator creating the reference image.
The present invention has been made in consideration of the above points and its object is to create an appropriate substrate reference image so as to appropriately perform defect inspection of a substrate.